Preoperative orthodontics for orthognathic surgery

Preoperative orthodontics for Orthognathic Surgery Prof dr maher Fouda BY Faculty of Dentistry Mansoura Egypt

Treatment time for the patient undergoing orthognathic surgery is prolonged . However, attempts by the orthodontist to cut corners in order to reduce treatment time, or by the surgeon to undertake surgery without adequate preoperative orthodontic preparation, will inevitably lead to problems, for the patient and the clinicians.

Clearly, time should not be wasted by the orthodontist in the preparatory phase of preoperative orthodontics , but accuracy in placing the teeth of both arches into the desired positions may well reduce the overall treatment time by reducing the length of postoperative orthodontics . Presurgical orthodontic preparation

F ive stages of orthodontic treatment are required for the patient undergoing orthognathic surgery, which are: 1. Preoperative orthodontics. 2. Immediate preoperative appointment. 3. Intraoperative orthodontic requirements. 4. Immediate postoperative appointment. 5. Postoperative orthodontics.

Prior to undertaking any form of orthodontic treatment , it is incumbent upon the orthodontist to ensure that the patient has optimal oral hygiene , and the absence of gingival inflammation , active periodontal problems, or any other dental disease, such as caries.

Any such issues must be managed prior to initiating orthodontic treatment. Good communication between the orthodontist and the general dental practitioner is important at this stage, and throughout treatment.

‘By failing to prepare, you are preparing to fail.’ Benjamin Franklin (1706–1790) (attributed) Preoperative orthodontics

The amount of preparatory orthodontic treatment required for the orthognathic patient is quite variable . It depends on the complexity of tooth movements required and the type of surgery being planned. For example, dental extractions and subsequent space closure are likely to be more time-consuming than non-extraction treatment.

Preoperative orthodontics

During the course of treatment planning, the dental and mandibular (skeletal) midline should be aligned with the mid-chin point. For the dental and maxillary midline, alignment with the middle of the chin is not necessary if Le Fort I osteotomy is planned for the maxilla . In this case, the dental midline can be corrected by a minor surgical rotation of the maxilla Dental midline corrections LeFort-1 osteotomy of the maxilla

Dental midline corrections often can be rather time-consuming, whereas a dental midline deviation planned to be corrected with rotation of the respective jaw requires less preoperative orthodontic preparation. Inevitably, this preparatory phase is the most prolonged phase of treatment.

Nevertheless, attempts to rush this stage will lead to potentially avoidable problems at the time of surgery. The time quoted to patients should be realistic, but, as a general rule, it is better to overestimate than underestimate the treatment time required , as patients are apt to remember!

Case MD with decreased lower facial height and skeletal deep bite. Intraoral Class II Div 2 malocclusion with retroclined incisors treated with mandibular advancement to reduce facial convexity and increase facial height. (A and B) Pretreatment facial photographs.

( C and D) Intraoral photographs. Presurgical decompensation aimed only at correcting the axial inclination of the incisors. (E and F) Levelling of curve of Spee is best achieved following surgery. (G and H) Post-treatment intraoral photographs. (I and J) Post-treatment facial photographs .

Types of orthodontic appliance The type of appliance used is essentially down to the preference of the orthodontist, though usually some form of preadjusted edgewise appliance is likely to be employed. The fixed orthodontic appliance is not only employed to achieve the desired tooth movements before and after surgery, but is also used by the surgeon to stabilize the jaws intraoperatively with intermaxillary fixation (IMF). Intermaxillary fixation types. (A) Surgical archwire fixation and (B) Orthodontic miniscrew fixation

Preadjusted edgewise appliance The former standard edgewise appliance employed relatively similar brackets on the teeth, and thereby required the orthodontist to place bends in the archwire edgewise bracket . (a) A first-order bend; (b) a second-order bend; (c) a third order bend . (a) edgewise bracket with a second order bend placed in the arch wire to achieve the desired amount of tip. (b) a pre-adjusted bracket with tip built into the bracket slot . finishing archwire incorporating individual tooth bends for an edgewise appliance .

The bends in the arch wires are used to individually position each tooth in terms of their relative horizontal ‘in–out’ positions, their crown angulation ( mesiodistal crown ‘tip’) and crown inclination ( buccolingual crown ‘torque’). This prepared archwire then engaged the brackets in an ‘edgewise’ manner, hence the name.

Preadjusted edgewise appliance In the mid-1970s, the American orthodontist Lawrence F. Andrews introduced the ‘Straight-wire appliance ’, which modified the standard edgewise system such that the information for the in-out position of each tooth, its crown tip and crown torque was incorporated into the respective bracket for each individual tooth, i.e. the details of the final tooth position is incorporated in each ‘ preadjusted ’ bracket.

Pre-adjusted Siamese edgewise brackets showing twin design and contoured base. The bracket prescription will position the tooth in three dimensions, generating mesiodistal tip, torque and in/out positioning .

A second-order bend, or an inclination of the bracket slot to produce the same effect, is necessary for the maxillary incisors because the long axes of these teeth are inclined relative to the incisal edge. The smaller angle is the bracket angulation or the tip.

This was achieved by varying the thickness of each bracket base (for the in-out position of the respective tooth), and by varying the angulation of each bracket slot relative to the long axis of each tooth in the mesiodistal plane (for the crown angulation) and contouring the base of the bracket occlusogingivally (for the crown inclination). First order or in and out bends built with the bracket PEA base Second order or mesiodistal tip incorporated into the bracket PEA Third order or torquing incorporated into to PEA bracket A) Torque in face, (B) Torque in base

Therefore, when the teeth are in their correct three-dimensional positions, there is a level bracket slot line-up, i.e. the bracket slots in each arch are at the same height, and there are no offset bends in the archwire . These preadjusted bracket systems have reduced the requirement for wire bending dramatically.

Nevertheless, accurate tooth positioning in preparation for surgery and effective postoperative finishing and detailing of tooth positions will almost always require some degree of wire bending . Much of the artistic flair(inclination) in orthodontic finishing still emanates from the orthodontist’s ability to bend wire . (a and b) A case . (c and d) In which the archwires were bended to improve intercuspidation (yellow arrows)

(a) First-order bend to buccally offset a maxillary canine tooth. (b) First-order bend to vertically extrude a maxillary first premolar.

(c) Second-order bend to correct the angulation of a maxillary first premolar. (d) Third-order bend to apply palatal root torque to a maxillary central incisor .

The most commonly used bracket slot sizes are the 0.018 × 0.025-inch (0.46 × 0.64 mm) and the larger 0.022 × 0.028-inch (0.56 × 0.7 mm). The type used is dependent on the preference of the orthodontist, but the 0.022 × 0.028-inch bracket slot does allow the use of heavier stainless steel archwires , which make dental arch levelling potentially easie r . Bracket slot dimensions and rectangular archwire dimensions in cross-section. A0.022 × 0.028-inch bracket slot is shown, with a 0.019 × 0.025-inch rectangular archwire .

Pronouncing bracket slot size and archwire dimensions To avoid long-winded terms in clinical practice, user-friendly abbreviations may be used at the chair side. The 0.018 × 0.025-inch bracket slot size is abbreviated and pronounced an ‘18-slot’, and the 0.022 × 0.028-inch bracket slot a ‘22-slot’. A round archwire , e.g. a 0.018-inch stainless steel, is pronounced ‘18-steel’, whereas a rectangular stainless steel archwire with the dimensions 0.019 × 0.025- inch is pronounced ‘19–25 steel’.

Banding vs. bonding of molar teeth In modern orthodontics, bonded brackets are the norm for all the teeth, although molar bands are occasionally used, particularly when transpalatal arches or tooth borne rapid maxillary expanders are required .

Some surgeons prefer the molar teeth to be banded, particularly the final tooth in each arch, which is usually the second molar.

Banding vs. bonding of molar teeth The reasoning is that should this tooth be bonded rather than banded, and thereby debond during surgery, it may be a potential problem. Alternatively, it may be argued that a loose band may not be noticed for some time.

Molar bands are also required if a band tube needs to be converted into a bracket , e.g. if a maxillary second molar tooth needs to be buccally offset or individually intruded, an archwire with the appropriate bend will not pass through a normal buccal tube on either a molar band or bonded buccal tube on the maxillary first molar. In such cases, the buccal cap of a convertible tube on the first molar band is removed, transforming the tube into a bracket . A convertible maxillary right molar band. The buccal cap of a convertible tube on the first molar band may be removed, transforming the tube into a bracket .

More recently, self-ligating molar tubes have been introduced, which may be used instead of a convertible tube Damon Q* self-ligating brackets bonded one month before surgery. Infrazygomatic miniplates inserted on both sides. B. Postsurgical overjet. C. Miniplates inserted in lateral mandibular body on both sides; Class III elastics worn from lower canines to upper second premolars.

A second, or auxiliary, archwire tube can be incorporated into a molar bond or band. This is useful in cases requiring segmental surgery, if an auxiliary wire needs to be constructed for placement into the auxiliary tubes to stabilize the segments immediately after segmental repositioning . Maxillary Double Convertible Heavy labial archwire secured through buccal tubes on banded maxillary molars to aid in maintenance of surgical expansion.

The use of lingual and palatal cleats on molar bands for attachment of elastics may be required in either the preoperative or postoperative phases; however, where bonded molar tubes have been used rather than molar bands, lingual or palatal buttons may be bonded directly onto the teeth if required. (A) Weldable lingual cleat. (B) Bondable lingual cleat

Labial vs. lingual appliance Labial orthodontic appliances are superior to lingual appliances in orthognathic patients for a number of reasons: Intraoperative IMF placement – Lingual appliances cannot be used by the surgeon intraoperatively for application of temporary intermaxillary fixation, and some form of labial attachment will be required, e.g. buttons or brackets bonded onto the labial aspects of the teeth, or temporary anchorage devices (e.g. microscrews ) in the labial alveolar bone . . Postoperative guidance elastics placed onto buttons with relief cutouts made in the clear aligners .

Labial vs. lingual appliance Debonding brackets – If a lingual bracket debonds during or immediately after surgery, it is very difficult to rebond in the immediate postoperative period, as the patient has discomfort, an inevitable degree of trismus leading to limited mouth opening, and often a mouth laden with blood-stained saliva.

Labial vs. lingual appliance Postoperative oral hygiene – The same factors may potentially make it more difficult for the patient to keep the teeth and appliances clean if the brackets are lingual. Anterior open bites – An upper lingual appliance may also interfere with complete overbite correction in anterior open bite cases. Orthodontic treatment initiated using a self-ligating lingual appliance Pretreatment facial and intraoral photographs

Use of aesthetic brackets Some patients may demand labial ‘aesthetic’ brackets, in which case informed consent is essential. However, routine stainless steel brackets and bands/tubes are superior to aesthetic labial brackets in patients undergoing orthognathic surgery, for a number of reasons: Susceptibility to fracture – Ceramic brackets are brittle and thereby vulnerable to fracture intraoperatively, particularly during placement of IMF. They also often shatter into pieces, in which case parts may potentially enter open surgical sites.

Use of aesthetic brackets Tooth wear – Ceramic brackets may also lead to serious tooth wear from abrasion with the enamel of teeth in the opposing arch, which may be a serious problem in orthognathic patients at the start of treatment due to the variety of presenting malocclusions, particularly deep bites, and may also become a problem during the preoperative period as the teeth align and decompensate .

Use of aesthetic brackets Plastic or resin composite type brackets – These are often difficult to see and may impede or reduce tooth movement due to problems of increased friction . They are also usually rather weak , and prone to fracture , which is again an intraoperative problem for which the surgeon will not be thankful.

Objectives of preoperative orthodontics If the teeth are crowded, spaced, rotated, incorrectly positioned, incorrectly angulated and inclined with respect to their basal bone, diagnosis and planning prior to the preoperative phase of preparatory orthodontics is essential, which forms the basis of the preparatory road map , required to reach the ultimate goal.

The orthodontist must have the precise destination in mind, in terms of where the teeth should be positioned in relation to the three planes of space, the three axes of rotation, and the eventual occlusion with the opposing dental arch before a single bracket is bonded .

The purpose of preoperative orthodontic treatment is to place the teeth into the correct position for their respective jaw, so that on repositioning the jaws, the surgeon may attain the desired skeletal movements and obtain the best possible dental occlusion.

The preparatory orthodontic tooth movements should be determined in relation to the proposed surgical movements of the jaws .

The intended tooth movements may be described in relation to the six objectives of preparatory preoperative orthodontic treatment : 1- Alignment 2- Levelling 3- Decompensation 4- Incisor inclination preparation 5- Arch coordination 6- Elimination of occlusal interferences .

These objectives of orthodontic preparation are not always achieved in the same order. For example, decompensation may occur prior to arch levelling, or maxillary arch expansion to coordinate the arches may be required at the beginning of treatment. In certain circumstances, some of these phases occur together.. An auxiliary archwire has been ligated over the main archwire .

1-Alignment Some authorities say that the best orthodontists of the past were those best at wire-bending, and that the best orthodontists of the present are those best at bracket positioning. Alignment is the straightening the teeth onto a horseshoe shaped wire

Such statements, however well-intentioned, are rather misleading. Accurate bracket positioning is vitally important, but some degree of wire-bending, particularly in the final stages of finishing orthodontics, is inevitably required.

1-Alignment The best orthodontists of the past, present (and future) are those who understand and apply the principles of accurate diagnosis and reasoned treatment planning, and develop technical cleverness in undertaking logically applied and biologically sound orthodontic mechanics.

1-Alignment Alignment is usually, though not always, the first step in preoperative orthodontics (arch expansion is sometimes undertaken prior to alignment). Some arch levelling also begins at the same time as alignment, i.e. when the initial archwire is engaged into the brackets the teeth will begin to level.

The purpose of alignment is to correctly angulate (‘tip’) the crowns of the teeth into the correct position for their respective jaw and to correct tooth rotations. 1-Alignment alignment is the lining up of teeth of an arch in order to achieve normal contact point relationships.

1-Alignment Bracket positioning – The brackets must be bonded into the correct position for each tooth. Time taken to accurately position the brackets at this stage is never wasted.

1-Alignment Minor variations in bracket positioning may be required in some orthognathic patients: Maxillary canines – In orthognathic patients, the coordination of the maxillary and mandibular labial segments, i.e. the canine-to-canine region, is paramount. Often, interference may occur between the tip of the mandibular canine and the mesio -palatal aspect of the maxillary canine, which prevents the intercuspation of the teeth.

1-Alignment Therefore, it is advisable to b ond the maxillary canine bracket approximately 1 ∕ 2 to 3 ∕ 4 of a millimetre mesial to the long axis of the tooth , leading to slight mesio -labial rotation of the tooth, and better ultimate interdigitation of the labial segment

( a) If the mesiopalatal aspect of the maxillary canine teeth is slightly prominent, it may prevent intercuspation of the anterior dentition, as in this postoperative Class III patient. (b) This may be prevented by bonding the maxillary canine bracket 1 ∕ 2 to 3 ∕ 4 of a millimetre mesial to the long axis of the maxillary canine in orthognathic patients with potentially reduced maxillary intercanine width . The slight mesio -labial rotation of the canine crown aids interdigitation.

1-Alignment Maxillary second molars – In many instances, these teeth should not be bonded, in order to prevent their extrusion, which will become a major interference in attempting arch coordination. If they must be bonded/banded, e.g. to derotate , then care should be taken to bonding the brackets somewhat occlusally . Evaluating the casts in a Class I relationship shows a true narrowness of the maxillary arch

1-Alignment If a convertible tube is placed onto the first molar, steps can be added to an arch wire to also minimise extrusion of the second molar .

1-Alignmen t Segmental surgery – In preparation for segmental surgery, some interdental space is required, both between the crowns and roots of the teeth on either side of the planned osteotomy, to permit space for the surgical cuts without damaging the teeth .

Segmental surgery design (a)to expand the intercanine width osteotomy is performed between canines and lateral incisors.Note the four incisor teeth in the anterior segment are almost in a straight line(black arrow) B ) interdental osteotomies between laterals and canines

(b) if the intercanine width is appropriate the interdental osteotomy can be positioned between the canine and first premolar A ) Interdental osteotomies between canines and premolars;

(c)A midline osteotomy is an option if the transverse deficiency is due to a v shaped arch

(d)A unilateral crossbite can be corrected with a unilateral osteotomy

1-Alignment The crowns of the teeth on either side of the planned osteotomy may be separated using active coil spring, but root divergence may be achieved by either having the brackets in the correct positions and placing second-order bends in the archwire , or bonding the brackets at an angle to diverge the roots, and rebonding them in the correct position postoperatively . Root divergence prior to segmental surgery . (b) a second-order bend

Selective bracket placement can create adequate interdental space for osteotomies. On the tooth mesial to the osteotomy, slightly rotate the mesial aspect of the bracket gingivally , and on the distal tooth, slightly rotate the distal aspect of the bracket gingivally . A straight wire will then diverge the roots .

1-Alignment If the surgical cut is planned distal to the canine teeth, contralateral canine brackets may be bonded, which reverses the tip in the brackets and angulates their roots mesially . Following surgery, the correct brackets may be bonded to correct the canine angulations. Interdental osteotomies between canines and premolars

1-Alignmen t Archwire size, shape and material – A thin, round archwire is ideal for initial alignment, producing little binding and friction, and permitting relatively free tipping of the tooth crowns. The forces should be as light as possible , whilst permitting tooth movement.

1-Alignmen t Nickel–titanium alloy ( NiTi ) is the initial aligning archwire material of choice , having both shape memory (i.e. it returns to its original form following plastic deformation, e.g. being ligated to a malpositioned tooth) and superelasticity (i.e. a flat ‘ superelastic ’ plateau in the middle of the force deflection curve, allowing appreciable distortion of the wire in order to engage brackets on considerably displaced teeth whilst maintaining acceptable force levels) .

The force-deflection curve comparing a nickel-titanium ( NiTi ) archwire with stainless steel. The almost horizontal plateau on the NiTi graph means that the wire will deliver approximately the same force over a large range of deflection . This highly desirable characteristic, known as superelasticity , is unique to NiTi archwires . In addition, the deactivation plateau is lower than the activation plateau, i.e. less force is delivered on unloading than is required to activate the wire (a property known as hysteresis ), allowing the use of light forces for initial alignment of the dentition .

The preliminary archwire is usually a round 0.014-inch, followed by a 0.016-inch NiTi or 0.018-inch copper NiTi after 1 to 2 visits of religation . 1-Alignment

Typical sequencing of archwires for an orthognathic patient is variable, depending on the desired 1-Alignment goals of treatment. Assuming a 0.022 × 0.028-inch bracket slot, the initial aligning archwire is usually 0.014-inch NiTi , moving onto 0.018-inch copper NiTi .

1-Alignment If sliding mechanics are required, e.g. to correct a dental midline shift, a working archwire of 0.018-inch stainless steel may be used, though a working wire should always be ligated into the brackets for at least a month, allowing levelling of the bracket slots, prior to any sliding mechanics being undertaken. This helps to make the archwire passive and thereby avoids binding of the brackets onto the archwire .

1-Alignment The 0.018-inch stainless steel archwire is also very useful for correcting the inclination of incisor teeth, as the teeth rotate round the transverse axis. If such movements are not required, then an interim 0.019 × 0.025-inch NiTi archwire is used to help prepare for the ligation of the 0.019 × 0.025-inch stainless steel archwires , on which surgery is usually carried out .

1-Alignmen t

1-Alignment

2-Leveling - The term leveling will be used to describe the process of bringing the incisal edges of the anterior teeth and the buccal cusp tips of the posterior teeth into the same horizontal plane ( Baldridge , 1969)

2-Levelling Dental arch levelling refers to the stage of orthodontic treatment which aims to flatten (or almost flatten) the curve of Spee , by permitting the relative vertical movement of the teeth in each arch to bring their marginal ridges to lie approximately in the same horizontal plane. Orthodontic levelling of an increased curve of Spee can be achieved as a combination of premolar/molar extrusion, incisor intrusion or incisor proclination .

2-Levelling A relatively flat (i.e. ‘level’) curve of Spee is one of the prerequisites to a normal dental occlusion.

2 -Levelling In the orthognathic patient, levelling may be undertaken at different stages of treatment, depending on the requirements of the respective case: Preoperatively – In the majority of patients most or all the levelling may be undertaken prior to surgery . Normal depth of Curve of Spee : 2-3 mm

2-Levelling Intraoperatively – The preoperative phase is used to segmentally align ‘segments’ of each dental arch and the segments are subsequently surgically levelled. The surgical technique of anterior segmental osteotomy

2-Levelling Postoperatively – Some or most of the levelling is undertaken following surgery, e.g. a 3-point landing ( interarch tooth contact at the incisors and terminal molars only) used to increase the lower anterior face height and reduce the incisor overbite . .

2-Levelling (a) Maintaining or creating an increased curve of Spee prior to mandibular advancement. (b) Mandibular advancement to a 3-point landing (incisors and terminal molars) occurs by a downward and forward vector of movement of the mandibular incisors. This will increase the lower anterior face height (LAFH) and(visualize) unfurl the mentolabial fold, improving the soft tissue contour of the lower face. The lateral open bites are closed orthodontically by extrusion of the mid-arch mandibular dentition, i.e. postoperative levelling of the curve of Spee .

2-Levelling The decision on how to level in the maxillary arch is predominantly based on the final desired position of the maxillary incisors in relation to the upper lip and face .

The curve of Spee in the mandibular arch the sagittal occlusal curve in the maxillary dental arch may be evaluated by holding each dental arch against the flat under surface of the opposing model .

2-Levelling Once the desired postoperative position of the maxillary incisors has been planned, the decision on how to level the mandibular arch depends on the planned postoperative position of the mandibular incisors in relation to the maxillary incisors and the effect of this position on the lower anterior face height (LAFH). If no increase in LAFH is desired, the mandibular arch is levelled preoperatively by incisor intrusion.

2-Levellin g However , if an increase in LAFH is desired , w the mandibular arch curve of Spee is either partially levelled if only a small increase in LAFH is desired, the curve is maintained if already present at the required depth, or the curve is accentuated if a significant increase in LAFH is desired, i.e. the degree of preoperative levelling depends on how much of an increase in LAFH is desired. As the mandible is advanced, the degree of anterior-inferior movement of the mandibular incisors will determine the increase in LAFH .

Levelling (c) If the LAFH does not need to be increased, the mandibular dental arch is levelled in the preoperative orthodontic preparatory phase, i.e. preoperative levelling of the curve of Spee . (d) As such, mandibular advancement does not lead to any significant change in the LAFH.

A tripod mandibular advancement(top left to top right) increases LAFH SLIGHTLY AS THE MANDIBLE ADVANCES .It does this because the curve of Spee is not leveled before surgery .Therefore the mandibular incisors are left stepped up(bottom),and they-ride down –the lingual surfaces of the maxillary incisors as the mandible is advanced increasing the LAFH .

2-Levelling Total continuous arch levelling – In most cases, total arch levelling will occur as the orthodontist moves through the archwire sequence into the flat, heavy rectangular stainless steel archwires . These will lead to extrusion of premolar and canine teeth, and intrusion of incisor and to a small extent terminal molar teeth, though the extrusive effect is always greater . Total continuous arch levelling . leveling of COS with the continuous archwire technique takes place by a combination of premolar extrusion and, to a lesser extent, by incisor intrusion.

2-Levelling However, if mandibular incisor intrusion is specifically desired, e.g. in a patient with an already increased LAFH, some form of orthodontic intrusion arch mechanics (e.g. Burstone mechanics) may be required, or temporary anchorage devices may be used to directly intrude the incisors.

2-Levelling Partial continuous arch levelling – e.g. maintenance of a degree of curve of Spee in preparation for a 3-point landing. There is some controversy over how great a lateral open bite may be closed . Relative intrusion is done by Reverse curve of Spee : It mainly causes extrusion of the posterior teeth. However there may be undesirable changes in the axial inclinations of the buccal teeth and flaring of the incisors.

3-point landing. (a) Preoperative images, demonstrating a Class II division 1 incisor relationship on a Class II skeletal pattern with mandibular retrognathia, a reduced lower anterior face height (LAFH) and increased curve of Spee .

2-Levelling (b) Preoperative lateral cephalometric radiograph and mandibular model, demonstrating maintenance of the increased curve of Spee .

2-Levelling ( c) Postoperative result with a 3-point landing, with contact at the incisors and terminal molars bilaterally. The mandibular 0.019 × 0.025-inch stainless steel surgical archwire is still ligated in position.

2=Levelling (d) A 0.017 × 0.025-inch flexible NiTi mandibular archwire is placed and box elastics are placed bilaterally to close the lateral open bites.

2-Levelling 12-weeks postoperative views, with lateral open bites essentially closed with postoperative levelling of the mandibular arch, and increase in LAFH .

2-Levelling There is a space requirement for levelling . An increased curve will need to be ‘wiped’ into the mandibular steel archwire to maintain or accentuate the curve of Spee preoperatively An increased curve has been ‘wiped’ into the mandibular 0.019 × 0.025-inch stainless steel archwire in order to maintain the mandibular curve of Spee prior to surgery .

2-Levelling Segmental arch levelling – For a patient being prepared for segmental surgery requiring levelling, the differential vertical movements required for each segment will depend on aesthetic and occlusal factors. In such cases the segments are aligned and levelled intra-segmentally, avoiding continuous initial aligning archwires .

A , Compensating steps (arrow) have been placed in the orthodontic arch wire so that the anterior teeth are aligned at an elevated level compared with the posterior teeth to eliminate extrusion or intrusion of teeth that may otherwise result in unstable orthodontic movements .

B , Sectioning the arch wire (arrow) is another approach to aligning teeth at separate independent levels to avoid extrusion or intrusion of teeth as seen in this maxilla. However, the use of sectional wires may decrease positional control of the teeth adjacent to the ends of the cut wire.

2-Levelling Subsequent stainless steel archwires may either remain segmental, or if continuous archwires are desired, they will require appropriate vertical bends placed between the segments

Segmental arch levelling in preparation for segmental surgery. Continuous stainless steel archwires with appropriate vertical bends placed between the segments. The active coil springs (‘ pushcoil ’) is cut to a length larger than the interbracket distance between the maxillary lateral incisors and canines that need to be slightly separated at their crowns. The pushcoil is compressed prior to insertion, generating the forces required .

2-Levelling Such continuous archwires will need to be cut intraoperatively to permit surgical manipulation of the segments. Stabilization of the segments will be required with a continuous archwire , perhaps placed into auxiliary molar tubes, immediately following surgical repositioning of the segments.

2-Levelling Space requirement for levelling – It is important to bear in mind that some space within each dental arch is required for orthodontic levelling. A space of approximately 1mm is required to level a 3 mm depth curve of Spee .

2-Levelling Therefore, if the maximum depth of the curve of Spee in the mandibular arch is 3 mm, then 1mmof space should be maintained in the mandibular arch to permit postoperative levelling by extrusion of the mandibular premolars and canines. More space is required for a greater depth of curve.

2-Levelling Space may be acquired by interdental enamel reduction or maintained from space closure following dental extractions. Alternatively, this space for levelling may be acquired by proclination of the mandibular incisors, which is the alternative to space creation in the mandibular arch, particularly in non-extraction cases .

Space requirement for arch levelling . Levelling an increased curve of Spee requires space. This may be gained by incisor proclination as demonstrated. If mandibular incisor proclination is to be avoided, space may need to be created by interdental enamel reduction, or a small degree of extraction space may be maintained preoperatively. In practice, the degree of space required is relatively small; approximately 1 mm of space (i.e. 0.5 mm per side) is required to level a 3 mm depth curve of Spee .

3-Decompensation The discrepancy between the jaws in all three planes of space has an indirect yet considerable influence on the dental occlusal relationship as a result of dentoalveolar compensation . Dentoalveolar compensation describes the variations in the positions of the teeth, in the sagittal, vertical and transverse dimensions, that may compensate for variations in the skeletal pattern , i.e. it is nature’s way of trying to get the teeth to meet when the jaws are growing away from one another . Dental compensation in skeletal Class II malocclusion Dental compensation seen in skeletal Class III malocclusion

Incisor compensation of class II Incisor decompensation 3-Decompensation

3-Decompensation In the normal situation, the erupting maxillary and mandibular teeth are guided towards each other by the surrounding soft tissue envelope of the tongue, lips and cheeks; hence, they erupt into a position of soft tissue equilibrium between the opposing forces of the tongue and lips/cheeks. The soft tissue envelope of the tongue, and lips/cheeks; the teeth are in a position of soft tissue equilibrium between the opposing forces of the tongue and lips/cheeks

3-Decompensation Therefore, in the presence of sagittal or transverse skeletal discrepancies, alterations in the inclination of the teeth compensate for the skeletal discrepancy. In patients with Class II occlusion the upper front teeth tend to lean back to compensate for the protruding jaw, while the lower incisors lean forward to compensate for a retracted jaw

(A) Typical compensations of anterior teeth in Class III patents. Proclined maxillary incisors and retroclined mandibular incisors. (B) The use of Class II elastics in Class III cases helps decompensate the anterior teeth. 3-Decompensatio n

Dentoalveolar compensation in the sagittal plane. (a) Proclination of the mandibular incisors often occurs to compensate for a Class II skeletal relationship; decompensation in preparation for mandibular advancement surgery would require their retroclination to a correct inclination for the mandibular skeletal base. (b) Proclination of the maxillary incisors and retroclination of the mandibular incisors may occur to compensate for a Class III skeletal relationship. Decompensation requires maxillary incisor retroclination and mandibular incisor proclination . 3-Decompensation

3-Decompensation In such cases, the occlusal discrepancy will appear less severe than the underlying skeletal discrepancy. For example, in a patient with a severe Class III skeletal pattern, the dentoalveolar compensation involves proclination of the maxillary incisors and retroclination of the mandibular incisors . Dentoalveolar compensation for a severe Class III skeletal discrepancy, with maxillary incisor proclination and mandibular incisor retroclination .

3-Decompensation This compensatory mechanism may be unsuccessful either because the skeletal discrepancy is too severe or because the soft tissue pattern is unfavourable . For example, in a Class II skeletal discrepancy, if the soft tissues are unfavourable and the lower lip is unable to control the labial aspect of the maxillary incisors and instead falls behind them it will lead to their proclination and thereby magnify rather than compensate for the skeletal discrepancy .

3-Decompensation In the vertical plane , the incisors will tend to overerupt to compensate for increasing lower anterior face height, unless a forward tongue position prevents their overeruption. If the face height is dramatically increased, the incisors may not be able to fully compensate and an anterior open bite (AOB) will ensue.

3-Decompensation Orthodontic preparation for orthognathic surgery requires orthodontic decompensation of the dental arches in all three planes of space , i.e. the process of removing the dentoalveolar compensations that may be present in the sagittal, transverse and vertical planes, and re-establishing the correct position of the teeth with regard to their own skeletal base thereby permitting adequate surgical correction of skeletal discrepancies .

Class II Pre-surgical orthodontic decompensation . In this Class II patient, the lower incisors were proclined and the upper incisors were upright initially. Pre-surgical orthodontics has corrected the incisor inclinations, resulting in an increased overjet . This in turn facilitates maximum skeletal correction . Class II Pre-surgical orthodontic decompensation 3-Decompensation

3-Decompensation and the planes of space and axes of rotation Decompensation in the transverse dimension is particularly important in patients with buccal crossbites , often associated with a hypoplastic maxilla and a Class III skeletal discrepancy.

3-Decompensation and the planes of space and axes of rotation If the dental compensation is mild, orthodontic expansion may be all that is required, though this is only possible for expansion up to 4–5 mm , and buccal root torque is required to prevent further buccal flaring of the maxillary molars.

If there has already been considerable dental compensation for the underlying skeletal discrepancy, this usually results in buccally flared maxillary molars and lingually inclined mandibular molars. 3-Decompensation and the planes of space and axes of rotation

3-Decompensation and the planes of space and axes of rotation Decompensation involves repositioning of the maxillary molars over basal bone, which increases the extent of the crossbite (a) Dentoalveolar compensation in the transverse plane of space. (b) Decompensation in the transverse plane will increase the relative transverse discrepancy

3-Decompensation and the planes of space and axes of rotation In such cases, surgical expansion of the maxilla may be required, together with only partial decompensation of the mandibular molars. Alternatively, a bilateral posterior crossbite may be accepted (a, b) Pretreatment Class III patient with broad mandibular dental arch. (c, d) Following maxillary advancement, accepting a planned bilateral posterior crossbite is not a functional or aesthetic problem as long as the maxillary arch is well-aligned and of average width .

3-Total vs. partial decompensation Total decompensation is usually required, in order to position the teeth correctly in relation to their respective skeletal base.

However, in some situations, it may be prudent to partially decompensate only, in order to reduce the extent of skeletal movements required where stability and relapse would be issues postoperatively.

3-Total vs. partial decompensation For example, when smaller skeletal movements are desired for facial aesthetic reasons, e.g. it may be planned to limit the extent of mandibular incisor proclination in preparation for a mandibular set-back procedure, in order to limit the degree of set-back .

3-Total vs. partial decompensation Another clinical situation where partial decompensation may be required is the maintenance or partial decompensation of lingually inclined mandibular molars in Class III patients. If the lingual inclination, i.e. dentoalveolar compensation, is maintained, crossbite correction will be easier . (a) Dentoalveolar compensation in the transverse plane of space. (b) Decompensation in the transverse plane will increase the relative transverse discrepancy .

3-Total vs. partial decompensation Morphological reasons may also dictate partial decompensation in some instances, e.g. insufficient alveolar bone thickness and/or a thin gingival biotype prone to gingival recession. This may be a particular problem in the mandibular incisor region

(a) Pretreatment views of a Class III patient with thin gingival biotype, demonstrating ‘washboard’(ridged wood for clothes ) appearance of the anterior tooth roots in the mandibular incisor and canine region. (b) Partial decompensation undertaken to limit the potential gingival recession and dehiscence as the mandibular incisors procline through thin labial alveolar bone. 3-Total vs. partial decompensation

Periodontal problems associated with proclination of the lower incisors during decompensation in a Class III skeletal case . Lower incisors and their periodontal evaluation 3-Total vs. partial decompensation

3-Total vs. partial decompensation Though free gingival grafts have been proposed prior to surgery in order to facilitate decompensation, their use is questionable, as the major problem is not lack of labial gingival tissue, but lack of labial alveolar bone. Consideration may be given to a free gingival graft following orthognathic treatment, for aesthetic reasons and to provide some protection to exposed root surfaces . Preoperative photograph showing Miller’s class III gingival recession in relation to #41 . Postoperative photograph showing graft sutured using 4-0 silk sutures at #41 region. Postoperative photograph showing graft sutured using 4-0 silk sutures at #41 region .

‘Worsening’ effect on dental occlusion and facial profile Just as dentoalveolar compensation tends to mask the extent of the underlying skeletal discrepancy, orthodontic decompensation unmasks/unveils(detects) the true extent of the underlying skeletal discrepancy . For example, a patient with a Class III skeletal discrepancy will often have retroclined mandibular incisors and possibly some proclination of the maxilla ry

‘Worsening’ effect on dental occlusion and facial profile As such, orthodontic decompensation results in retroclination of the maxillary incisors and proclination of the mandibular incisors, thereby increasing the reverse incisor overjet and making the lower lip more prominent . ‘Worsening’ effect on the facial profile following orthodontic decompensation. (a) Pretreatment views of a Class III patient. (b) Mid-treatment views following incisor decompensation, with greater prominence of the lower lip.

‘Worsening’ effect on dental occlusion and facial profile This is one aspect of treatment that may displease patients a great deal. As such, it is extremely important that patients are made aware of this issue prior to embarking on treatment, and as part of informed consent .

Retraction vs. retroclination of incisors Orthodontic retraction and retroclination are not the same thing, and are not achieved with the same mechanics. Retraction describes the bodily translation of the incisor teeth in a lingual/palatal direction. Retroclination describes the rotation of the incisor teeth round the transverse axis of rotation, with the crown moving lingually / palatally . Vertical loop retraction arch ; Mini-implant and 3-mm soldered hook ; Mini-implant and 6-mm soldered hook. Controlled tipping ;

Retraction vs. retroclination of incisors These movements arise from different orthodontic mechanics, which must be accurately planned. If the incisors are protruded, then they are retracted within the limits of the surrounding alveolar bone; if the incisors are proclined , they are retroclined to the correct or required inclination . Space closure using sliding mechanics.

Retroclination of incisors is undertaken on round stainless steel archwires , with elastomeric chain around the incisor brackets if there is interdental spacing, and intratraction .

Retroclination is undertaken on round stainless steel archwires . (a) Pretreatment view. (b) Mid-treatment view, following initial alignment and some decompensation of the mandibular arch. An upper 0.018-inch round stainless steel archwire is placed, with circle loops positioned between the lateral incisors and canines in order to provide a point of attachment for elastic intra-arch traction. (c) Retroclination of the maxillary incisors using the described mechanics.

Retraction vs. retroclination of incisors Retraction of incisors is undertaken with rectangular archwires . In some situations, the incisors may need to be retroclined to the correct inclination, then retracted to the correct sagittal position, in which case the former is carried out on a round stainless steel archwire (usually 0.018-inch) and the latter with a rectangular stainless steel archwire . Comparison of incisor retroclination and retraction. (a) Incisor retroclination should be undertaken on a round archwire , which permits rotation of the tooth, in order to correct its inclination. (b) Incisor retraction should be undertaken on a rectangular archwire , which permits bodily translation of the tooth with minimal change in inclination .

Interarch elastics Either Class II or Class III elastics may be required in order to help incisor proclination / retroclination . However, their use is the opposite to a conventional orthodontic case , i.e. in a patient with a Class III skeletal pattern, Class II elastics are used to retrocline /retract the maxillary incisors and procline the mandibular incisors

(A) Typical compensations of anterior teeth in Class III patents. Proclined maxillary incisors and retroclined mandibular incisors. (B) The use of Class II elastics in Class III cases helps decompensate the anterior teeth

(a) These check models, taken for a class II patient during pre-surgical orthodontics, revealed that the buccal segment occlusion would be class II, due to incomplete incisor decompensation. (b) Inter-maxillary traction with class III elastics, aimed at retroclining the lower incisors and proclining the uppers enabled class I buccal segments to be achieved in the final result (c)

Interarch elastics Conversely, in a patient with a Class II skeletal pattern, Class III elastics are often required to retrocline the mandibular and, if necessary procline the maxillary incisors, thereby increasing the incisor overjet in preparation for surgery . (a) In a Class II patient, Class III elastics may be used to help incisor decompensation. (b) In a Class III patient, Class II elastics may be used to help incisor decompensation.

Extraction patterns Dental extractions, when required, will be so as to permit the maximum extent of decompensation achievable, and thereby allow the desired extent of surgical movement of the jaws . In preparation for orthognathic surgery dental extraction patterns are usually the opposite of those used in conventional orthodontics .

The Class II orthognathic patient with proclined mandibular incisors often requires extraction of mandibular first premolar teeth, to permit maximum retroclination and retraction of the mandibular incisors.

Extraction patterns In a Class III orthognathic patient, the extraction pattern is usually maxillary first premolars only to allow retroclination and retraction of the maxillary anterior dentition. The mandibular dental arch is usually treated on a non-extraction basis, as proclination of the mandibular incisors provides space for alignment .

Extraction patterns Dental extraction pattern in a Class III patient. (a) Pretreatment views. The incisors are compensated for the skeletal Class III jaw relationship. Orthodontic decompensation required extraction of a premolar in each maxillary quadrant (right second premolar was extracted as significantly displaced palatally ). (b) Retroclination of the maxillary incisors on a round 0.018-inch stainless steel archwire until the incisors were of the correct inclination .

Extraction patterns (c) Retraction of the incisors on a rectangular 0.019 × 0.025-inch stainless steel archwire . The mandibular arch was aligned and decompensated on a non-extraction basis. Incisor inclinations are correct to their respective skeletal bases and there is a significantly increased reverse incisor overjet in preparation for surgery. (d) The effect of decompensation on the facial profile, particularly lip prominences, may be observed. (e) Pretreatment lateral cephalometric radiograph compared with (f) preoperative radiograph, demonstrating incisor decompensation

A and B extraction pattern for class III malocclusion ( A ) for routine orthodontics ,( B) for surgical orthodontics .Extraction of upper first and lower second premolars is carried out . mandibular second premolars may need to be extracted to create space to contract a broad mandibular arch. All extraction patterns should be planned after undertaking a comprehensive space analysis . However, if required , Extraction patterns

A and B extraction pattern for class II malocclusion.( A ) for routine orthodontics , ( B ) for surgical orthodontics .This is to prevent over retraction of the maxillary anterior teeth which would compromise the mandibular advancement and lower first premolar extraction should be planned to allow leveling of the arch and to correct the lower anterior proclination . Extraction patterns

In a Class II orthognathic patient, the greatest anchorage requirement is usually in the mandibular arch, for retroclination and retraction of the mandibular incisors Anchorage requirements

In the Class III orthognathic patient, the maximum anchorage requirement is usually in the maxillary dental arch, for retroclination and/or retraction of the maxillary incisors. Anchorage requirements

4-Incisor inclination preparation The orthodontic treatment required to prepare the maxillary and mandibular incisor inclinations for surgery often occurs as part of incisor decompensation. However, preoperative incisor inclination changes are not always, by definition, strictly speaking decompensation.

4-Incisor inclination preparation For example, Class II patients with mandibular retrognathia often develop a lower lip trap, i.e. the lower lip gets caught behind the maxillary incisors, and leads to their proclination . This is not a compensatory proclination , but the inclination of the maxillary incisors needs to be corrected prior to mandibular advancement surgery.

4-Incisor inclination preparation Incisor inclination preparation for orthognathic surgery depends on whether surgery is being planned for a jaw, and whether that surgery involves rotation of the jaw round the transverse axis .

If surgery is not being planned, then the incisor inclination for that jaw should be corrected prior to surgery, e.g. proclined maxillary incisors should be corrected preoperatively when only mandibular advancement surgery is being planned .

4-Incisor inclination preparation If surgery is being planned for either jaw that will only entail sagittal bodily translation of the jaw, or if only vertical maxillary movement is required, then the incisor inclination for that jaw should again be corrected prior to surgery.

4-Incisor inclination preparation However, if either jaw is being planned for surgery that will involve the rotation of the jaw round the transverse axis , such as differential posterior impaction of the maxilla, or autorotation of the mandible, which thereby alters the inclination of the incisors, then the incisor inclination should be prepared preoperatively to take into account the change in incisor inclination that will occur as part of the surgical repositioning of the respective jaw .

4-Differential posterior maxillary impaction In patients with an anterior open bite, the preparation for a Le Fort I differential posterior impaction of the maxilla requires the creation or maintenance of a predetermined amount of maxillary incisor proclination . As the posterior maxilla is superiorly repositioned by a greater amount than the anterior maxilla, the maxillary incisors are effectively retroclined to the correct inclination . Maxillary incisor inclination alters with differential impaction of the maxilla .

Mandibular incisor inclination and mandibular autorotation If any form of superior or inferior repositioning of the maxilla is being contemplated, the effect on the mandible should be borne in mind. As the maxilla is superiorly repositioned, the mandible will autorotate forward (in the direction of mouth closing), reducing the inclination of the mandibular plane .

Mandibular incisor inclination and mandibular autorotation In preparation for this, the mandibular incisors will often need to be slightly proclined prior to surgery ( the opposite is true in preparation for inferior repositioning of the maxilla). .

A useful guideline is that the inclination of the mandibular incisors to the mandibular plane should be approximately 120 ◦ ; therefore, as the mandible autorotates forward, reducing the mandibular plane inclination, the mandibular incisor inclination increases , and vice versa 120 ◦

Mandibular incisor inclination preparation for mandibular autorotation. If the mandibular incisor inclination is not orthodontically prepared prior to forward mandibular autorotation, the incisor inclination will be incorrect following autorotation .

The mandibular incisor inclination has been orthodontically prepared (in this case by proclination ). In this situation, the mandibular incisors may appear excessively proclined , but clinicians should be aware that this is their planned position . With forward autorotation of the mandible ; the mandibular incisor inclination will be correct.

5-Arch coordination Dental arch coordination refers to the aspects of orthodontic treatment which ensure that the maxillary and mandibular dental arches will fit well together in occlusion, with maxillary and mandibular arch forms that correspond to one another, and with normal incisor, canine and buccal segment overjet . Preliminary evaluation of arches coordination by positioning the casts in molars class I relationship Evaluating the casts in a Class I relationship shows an acceptable transverse coordination

Coordination of the maxillary and mandibular dental arches is achieved by a combination of expansion of one arch (usually the maxillary) and/or contraction of the opposing dental arch .

(A) pre-orthodontic study models ,( B) posterior transverse and anterior midline discrepancies after hand articulation of pre-orthodontic treatment study models in the anticipated post- surgical position .( C, D) After completion of pre- surgical orthodontic treatment with extraction of maxillary right and left first premolars and decompensation of malocclusion . Note the coordination of the posterior dental arch width and the maxillary and mandibular midlines .

Hand articulating the models to simulate the occlusion with surgery a- pretreatment occlusion b-hand articulating the models without orthodontic treatment c- presurgical occlusion after orthodontic treatment d- hand articulating the models will show that with surgery there is good occlusal stability and the patient can now scheduled for surgery .

5-Arch coordination Of all the parameters that must be dealt with in orthodontic preparation, the coordination of the maxillary arch with the mandibular arch is often the most important, commonly the most challenging, and usually the most likely to cause problems at the time of surgery and in the postoperative phase of treatment . Dental casts showing surgical occlusion of a patient. (Top) Maxillary (left) and mandibular (right) casts; red indicates midlines. (Bottom) Surgical occlusion showing the coordination of the maxillary and mandibular jaw midlines; red indicates midlines.

5-Arch coordination Ideally, the dental arches should be as well coordinated as possible prior to surgery. However, in some patients, if the occlusion is so well-interdigitated as to make expansion difficult, particularly in low angle patients, glass ionomer cement blocks may be placed on the occlusal surface of the maxillary first or second molars to disclude the arches, and permit easier expansion .

Judging arch compatibility can be difficult In mandibular advancement, arch compatibility can be judged clinically. In maxillary advancement or mandibular setback, compatibility can only be judged with study casts.

5-Arch coordination Conv ersely, some of the posterior buccal segment expansion (perhaps 3–4 mm, i.e. no more than 2 mm per side) may be completed postoperatively. However, t he coordination of the canine-to- canine region of the maxilla to that of the mandible is the single most important preparatory requirement of preoperative orthodontics . Good preoperative coordination of this region is mandatory(imperative).

5-Arch coordination The aims of preparatory orthodontic treatment in relation to arch coordination are twofold: 1. To expand or contract the maxillary and mandibular dental arches as required, so they will adequately conform to one another at the time of surgery; and 2. To prevent undesirable expansion or contraction in either arch.

5-Arch coordination Prior to initial orthodontic appliance placement, the pretreatment diagnostic study models should be hand articulated such that they are held in the approximate proposed postoperative position of the skeletal bases. This will provide some idea of the degree of arch expansion or contraction that may be required (a) Pretreatment study models in pretreatment occlusion. (b, c) Hand articulated pretreatment study models in the approximate postoperative position of the skeletal bases will provide an idea of the degree of arch coordination that will be required .

5-Arch coordination Additionally, the buccolingual inclination of the molar and premolar teeth relative to their respective skeletal base should be observed : Maxillary dental arch – If the maxillary molars and premolars are at a correct inclination relative to the skeletal base, but the arch is narrow, it will need to be expanded whilst preventing buccal flaring. However, if the buccal segment teeth are already flared, their inclination will need to be corrected, and thereby the maxillary arch is likely to require even greater overall expansion . If the maxillary posterior dentition is already buccally inclined, correcting their inclination will increase the amount of overall expansion required in the maxillary arch.

Mandibular dental arch – If the mandibular molars and premolars are lingually inclined, particularly in Class III cases with broad mandibular arches, their inclination may need to be maintained , by using transversely contracted round archwires or contracted rectangular wires with lingual crown torque in the buccal segments . 5-Arch coordination

Placement of regular rectangular archwires will very quickly lead to buccal crown movement of these teeth, increasing the mandibular intermolar width and making arch coordination difficult.

5-Arch coordination . (a) Lingually inclined ( lingually ‘rolled’) mandibular molars (this represents dentoalveolar compensation in the transverse plane). (b) Pretreatment occlusal view of the mandibular arch demonstrating lingually inclined mandibular molars. (c) Placement of a mandibular rectangular archwire demonstrates the degree of buccal inclination and increase in intermolar width that will occur; compare the position of the first molar, which has moved buccally , and the obvious step with the second molar, which is still in the pretreatment position

5-Arch coordination The alternative is to allow the torque expression in these teeth to occur, but to accept a bilateral posterior crossbite at the end of treatment .

5-Arch coordination If preoperative maxillary arch expansion is required, a number of methods are available: Expanded archwires – In many cases, expansion in the maxillary dental arch, and the coordination of the maxillary and the mandibular arches to one another, may be best accomplished using coordinated archwires . A maxillary 0.019 × 0.025-inch rectangular expanded archwire prior to ligation, demonstrating degree of expansion per side .

Dentoalveolar maxillary expansion with a straight rectangular TMA® wire. (a) The straight TMA® wire is inserted into brackets and buccal tubes on the right to left maxillary first molar. (b) Wire ligatures are used for attachment to all brackets

beta-titanium auxiliary expansion archwire (TMA-EA ) The TMA-EA was made using a straight 0.032-in beta-titanium wire with tear-form hooks on both ends to facilitate its engagement in the 0.016 x 0.022-in NiTi thermo archwire . The TMA-EA was maintained as a straight segment, thus not contoured in an arch form, to induce buccal traction of the NiTi thermo archwire and consequently the dentoalveolar process

The length of the TMA-EA was calculated by measuring the perimeter between each mesial entrance of the molar tubes. The hooks of the TMA-EA were engaged with the main archwire at the interproximal area between the second premolars and the first molars.

Additionally; stainless steel ligature ties (0.008 in) were placed at the central incisor and premolar areas to improve the stability of the TMA-EA. During each appointment, the ligature wires were cut, and the TMA-EA was removed and straightened.

The initial aligning archwires cannot be coordinated , but expanded arch forms in NiTi archwires will help expand where necessary – this effect is more pronounced with lower friction type bracket systems, such as self-ligating brackets (possibly due to the broader arch forms of the initial archwires ), or the tying of brackets loosely with stainless steel ligatures. Tight elastomeric ligatures may limit such movement due to increased friction.

However, as soon as stainless steel wires are used, their widths may be coordinated. Though round archwires may be useful in particularly difficult cases, e.g. an expanded 0.020-inch stainless steel, their downside is to buccally flare the maxillary molars and potentially cause hanging palatal cusps.

As such , coordinated rectangular stainless steel archwires will eventually be required as the buccal root torque expression helps to limit buccal flaring, to elevate hanging palatal cusps and correct the inclination of the posterior teeth relative to their basal bone.

Removable appliances – A removable appliance with a midline expansion screw is an excellent method of maxillary arch expansion . Adams claspsare attached on the maxillary first molars and first premolars for retention. An expansion protocol of 1 ∕ 4 turn of the jackscrew per week , which equates to a 0.2 mm of expansion, may be used in adults . .

of the maxillary molars, compared to other types of expansion, though this is not an evidence-based statement. It is important to maintain the expansion while moving into the fixed appliance Clinical experience with this method appears to suggest reduced buccal flaring

Once the maxillary arch has been expanded, the Adams clasps may be removed from the first premolar teeth and the removable appliance wear continued, and the upper arch, excluding the molars, is bonded and aligned. Once reaching into a round 0.018-inch stainless steel archwire , which is sturdy enough to maintain the expansion, the removable appliance is discarded and the molars bonded and aligned.

The orthodontic (or orthopaedic ) jackscrew consists of a threaded cylinder . The pitch of the screw thread is set so that a complete 360 ◦ turn of the screw will produce a separation of 0.8 to 1.0 mm. A small key may be inserted into the holes in the centre of the screw allowing for one quarter turn incremental adjustments. Therefore, each turn of the screw equates to 0.2 to 0.25 mm .

Auxiliary archwires – Also known as jockey arches , these auxiliary wires may be easily constructed at the chair side and incorporated into a fixed appliance during treatment. They can also be used to maintain arch width after rapid maxillary expansion . An auxiliary archwire has been ligated over the main archwire .

The expansion arch, which can be made from 0.019 × 0.025-inch stainless steel or a larger round steel wire with a diameter of 1–1.13 mm, runs over the main archwire and is inserted into the headgear or auxiliary tubes of the first molar bands posteriorly and secured anteriorly with a ligature .

Some operators prefer to bend the wire into the buccal sulcus in order to reduce its visibility. Expansion is likely to be produced by a degree of buccal molar flaring and this may be reduced by incorporating molar buccal root torque into the main rectangular archwire .

Quadhelix (or trihelix in cleft patients or severely narrow maxilla) – This is a modification of Coffin’s W-spring, which incorporates four helices to increase flexibility and range of activation. The length of the palatal arms may be altered, depending on which teeth other than the first molars need to be expanded .

trihelix in cleft patients or severely narrow maxilla

The majority of expansion in an adult will be due to buccal molar flaring. In patients with a very narrow palate and maxilla, a trihelix may be used . An overall activation of 8mm(i.e. 4mmper side) provides approximately 400 grams of force for expansion. Trihelix appliance for expansion of a severely narrow maxilla in a patient with cleft palate .

Rapid maxillary expansion (RME) – Rapid maxillary expansion was first described by the American dentist Emerson C. Angell (1822–1903) in 1860, to laterally expand the maxilla by bony separation Emerson C. Angell (1822–1903) expanded the maxilla by bony separation across the midpalatal suture .

The technique was later re-popularized by the orthodontist Andrew Haas. The aim of this technique is to improve the ratio of skeletal to dental lateral movement by producing sutural expansion at the midpalatal suture . .

the time allowed for dental movement and carrying out treatment during or before the pubertal growth spurt This is achieved by using a rigid appliance, which will limit buccal flaring of the molars, expanding the midpalatal suture rapidly using high forces to limit

Following puberty, there is greater interlocking of the maxillary sutures which may limit their separation. As a general rule, rapid maxillary expansion is indicated in cases with a transverse discrepancy equal to or greater than 4 mm, and where the maxillary molars are already buccally inclined to compensate for the transverse skeletal discrepancy.

Approximately 40% of the expansion achieved may be attributed to skeletal changes. The ratio between anterior ( intercanine ) to posterior ( intermolar ) skeletal expansion has been found to be approximately 2:1 and the greatest skeletal response is achieved when treatment is carried out before or during puberty .

Rapid maxillary expansion (RME) in a patient planned for eventual orthognathic surgery. (a) Pretreatment views demonstrating narrow maxilla and lingually inclined mandibular molars. (b) Banded RME appliance in situ; an expansion screw key is used to turn the Hyrax ( Hy gienic Rapid Ex pansion ) screw .

3 weeks review demonstrating expansion and formation of a maxillary midline diastema. The maxillary standard occlusal radiograph demonstrates opening of the midpalatal suture. To prevent the screw from turning backwards it is stabilized with glass ionomer cement. (d) Removal of the RME appliance after 3 months and placement of a transpalatal arch (TPA) with arms to maintain the expansion. The midline diastema has closed spontaneously due to the action of the transseptal fibres .

RME in an orthodontic patient with narrow maxillary arch and crowding. (a) Pretreatment. (b) Following RME and fixed orthodontic appliance treatment. As well as creating a broader smile, space is created by the RME for alignment.

The posterior maxilla expands less readily because of the resistance produced by the zygomatic buttress and pterygoid plates.

Surgically assisted rapid maxillary expansion (SARME) – ( also referred to as surgically assisted rapid palatal expansion or SARPE) – This technique may be considered in skeletally mature individuals with significant transverse discrepancies. Diagram showing bilateral from piriform rim to low in area of pterygopalatine junction. Dissection through the connective tissue from epithelial incision to periosteal incision beveled in order to create a pocket-like tissue wound

The main resistance to maxillary skeletal expansion comes from the buttressing effect of the zygomatic and sphenoid bones at their point of attachment to the maxilla and from the integrity of the midpalatal suture. With SARME, these attachments are surgically severed, which allows expansion to be easily achieved using a conventional RME appliance . Diagram showing separation of maxillae with osteotome driven between the incisors. Diagram showing mobilization ofthe maxilla by twisting the osteotome . After marking the osteotomy route with a tiny round bur

Latency is considered to be the time interval between osteotomy and the appliance start-up and varies from 0 to 14 days in experimental and clinical studies . Activation rate is the amount of daily bone distraction (in millimeters); it varies from 0.25 to 1.0 mm De Freitas et al recommend the expansion procedure with an overexpansion index of 23% above the desired measurements to compensate for relapse Retention period at the end of the distraction is necessary for the neoformed bone tissue to acquire the necessary resistance to bear the tipping forces. T his period can vary from one to six months

Fixed appliances can be used to move apart the roots of the central incisors before surgery to avoid their damage by the midline maxillary cuts. Expansion is typically carried out at a rate of 0.4 mm per day (one turn of the screw in the morning and one turn in the evening ) and patients develop a significant midline diastema .

Surgically-assisted rapid maxillary expansion (SARME). (a) Pretreatment views demonstrating severe transverse maxillary deficiency. (b) Intraoperative view showing Le Fort I surgical cuts before the midline maxillary cut is made to mobilize the maxilla. (c) A 10 mm diastema was created during SARME. (d) Spontaneous closure of the diastema during the retention period .

Surgically-assisted rapid maxillary expansion (SARME). (a) Pretreatment. (b) RME appliance in situ prior to surgery. (c) 3-months following surgery. (d) 9-months following surgery and fixed orthodontic appliance treatment, with transpalatal arch (TPA) to help maintain the expansion. The patient is being prepared for bimaxillary surgery. A maxillary standard occlusal radiograph demonstrates bony infill of the midpalatal region.

The diastema will close spontaneously by mesial tipping of the maxillary incisors, and root alignment and final space closure is accomplished with subsequent fixed orthodontic appliances. Surgical expansion has a high relapse tendency, probably because of the inelasticity of the palatal mucoperiosteum , and a degree of over-correction is valuable.

Arch form – The pretreatment arch forms may be acceptable, or may need to be altered. In Class III orthognathic patients with a retrusive maxilla, the maxilla tends to be hypoplastic as well. As such, the maxillary dental arch often needs to be expanded .

In the Class II orthognathic patient, the maxillary arch form may be tapered and narrow in the premolar and canine regions. In such cases, the archwires will inevitably expand the canine-premolar regions due to their arch form. When intermolar width is constricted, expansion with archwires is usually not sufficient, and other forms of arch expansion should be considered.

(a) In this Class II orthognathic patient, the maxillary arch form is tapered and narrow in the premolar and canine regions, sometimes referred to as a V-shaped arch. (b) Postoperative view following orthodontic treatment and mandibular advancement surgery, demonstrating expansion and ‘rounding out’ of the maxillary arch, creating a U-shaped arch .

Effect of sagittal jaw movement on transverse arch coordination – It is important to bear in mind that sagittal movement of the maxillary arch in relation to the mandibular arch has an effect on their mutual transverse relationship, i.e. one is moving the broader posterior aspect of the maxillary arch forward relative to a narrower aspect of the mandibular arch. Therefore, in a Class II orthognathic patient, the broader posterior aspect of the mandibular arch is advanced against a narrower part of the maxillary arch .. Presurgical and hand-articulated study casts simulating mandibular advancement Class II deep bite-low angle patient

Conversely, in a Class III orthognathic patient, a broader part of the maxillary arch is often advanced relative to a narrower part of the mandibular arch

Sagittal movement of the maxillary arch relative to the mandibular arch has an effect on their mutual transverse relationship, i.e. the broader posterior aspect of one arch is advanced relative to a narrower aspect of the opposing arch. As such, arch coordination should always be undertaken in relation to the desired postoperative sagittal position of the skeletal bases. (a) Position of the mandibular arch (green) relative to the maxillary arch (red) in a Class II patient. (b) Following mandibular advancement the broad posterior aspect of the mandibular arch moves forward relative to a narrower part of the maxillary arch. In such cases, the maxillary arch should be expanded preoperatively, and the arches coordinated.

Extraction patterns – As far as possible, it is better to avoid extracting in the maxillary arch in Class III cases, as the inevitable contraction of the arch resulting from reduced tooth tissue can make coordination with the inevitably broader mandibular arch difficult. .

Class III cases do not usually require extractions in the mandibular arch, crowding is generally rare because of the increased arch length associated with an enlarged mandible and space is often generated as a result of the incisor proclination required for decompensation.

In contrast, space is often at a premium in the maxilla, arch length can be reduced because of a small and narrow upper jaw and there is commonly crowding. To make matters worse, the incisors often require some retroclination , which requires space, and therefore premolar extractions are commonly required

Conversely, occasionally the extraction of second premolar teeth may be undertaken in the excessively broad mandibular arch to provide space for arch contraction.

Extraction of ectopic maxillary canines and orthodontic repositioning of the first premolars into the canine position. (a) Pretreatment views. Following decompensation the patient underwent a maxillary advancement. (b) End of treatment views If the maxillary canine teeth are excessively ectopic, consideration may be given to their surgical removal, and orthodontic space closure, moving the first premolars into the canine space .

Additionally, if the maxillary lateral incisors are missing, the canines may be placed in the lateral incisor positions and masked, so long as their crown height is not excessively increased, and their colour is not too dark Missing maxillary lateral incisors and orthodontic repositioning of the canines into the lateral incisor positions, and reshaping of the canines. (a) Preoperative views.

(b) End of treatment views, following maxillary advancement and slight mandibular set-back .

As a general guideline, teeth may be orthodontically repositioned away from their normal locations in the dental arch as long as arch coordination may be maintained and smile aesthetics is not adversely affected .

Evaluating arch coordination during treatment The Class II orthognathic patient may be asked to posture their mandible forward, to get an idea of the labial segment (canine-to-canine) interdigitation . The intermolar and interpremolar widths may be estimated visually, as these teeth will not meet their opposing arch by mandibular anterior posturing. .

Class III patients cannot posture in such a fashion, but assessing coordination is just as important

A relatively simple technique is to take an impression of the mandibular arch and from it to create an acrylic model of the cusp tips, which may be held against the maxillary arch to check arch coordination Checking arch coordination in the Class III patient mid-treatment may be accomplished by creating an acrylic model of the mandibular arch .

Towards the end of treatment, the ideal way to check arch coordination is to remove the final archwires and take a set of impressions, from which may be cast the so-called ‘snap models’ or ‘snaps’. These are then hand articulated to assess the potential postoperative ‘fit’ of the teeth. Self-cure acrylic slurry being poured into the impression, prior to placement in water bath. Class III presurgicaL malocclusion with asymmetric mandibular prognathism . Acrylic model of lower arch Clinical assessment of arch coordination.

Elimination of occlusal interferences Planning to prevent occlusal interferences begins before a single bracket is bonded. Additionally, during treatment the dental arches should be checked at every visit, in order to continue preventing the formation of potential interferences, and eliminating them when they occur.

When interferences are discovered, the orthodontist should resist the temptation of ignoring them, and would be ill-advised to abandon it to be dealt with postoperatively. Interferences can make the operative attainment of a good occlusal result impossible, and worse still, may impede accurate surgical repositioning of the jaws. Delaying surgery while potential interferences are eliminated is the right course of action, and will almost certainly reduce the length of postoperative orthodontics.

It is vitally important to check the patient’s individual dental arches and their occlusion with keen observation and with interim ‘snap models’ when required , in order to detect potential occlusal interference. (a) Preoperative view of a Class III patient. (b) Archwires are removed prior to taking impressions for snap models.

‘Snap’ dental models may be used to check for any potential occlusal interferences during the preparatory stages of orthodontics, and particularly preoperatively. It is preferable to take the impressions for snap models without the archwires , which permits better visualization of the dentition on the models.

(c) Snap models in preoperative occlusion. (d) Snap models are hand articulated into the proposed postoperative position, demonstrating potential interferences (d) in the right canine region and (e) the left premolar region .

: In the Class III orthognathic patient with maxillary hypoplasia or mandibular macrognathia , coordinating the labial segments is often difficult. The orthodontist may use expanded arch forms for the anterior maxilla and contracted arch forms for the archwires in the anterior mandible. If this not enough, canine offsets may be placed in the maxillary archwire . (a) Canine offset bends in the archwire to permit better coordination of the anterior dentition. (b) Postoperative occlusion . The most common potential interferences in orthognathic patients are the following

Alternatively, some pushcoil may be used between the maxillary lateral incisors and canines, to expand the maxillary intercanine width. The space created can be closed postoperatively.

Another important parameter is the morphology of the mesiopalatal region of the maxillary canine . If this region is pronounced, the maxillary canine bracket should be bonded 1 ∕ 2 to 3 ∕ 4 of a millimetre mesially , in order to rotate the maxillary canine teeth mesiobuccally . (a) If the mesiopalatal aspect of the maxillary canine teeth is slightly prominent, it may prevent intercuspation of the anterior dentition, as in this postoperative Class III patient. (b) This may be prevented by bonding the maxillary canine bracket 1 ∕ 2 to 3 ∕ 4 of a millimetre mesial to the long axis of the maxillary canine in orthognathic patients with potentially reduced maxillary intercanine width. The slight mesio -labial rotation of the canine crown aids interdigitation .

Extrusion of maxillary second molars – It is vitally important to avoid extrusion of maxillary second molar teeth. If they are already extruded, a small amount of glass ionomer cement on their occlusal surface will lead to their slight intrusion ; the material may be removed postoperatively. Glass ionomer cement has been placed on the occlusal surface of the maxillary second molar teeth in order to intrude them.

Alternatively, if they must be included in the appliance, they should be bonded slightly occlusally If maxillary second molars have to be bonded/banded, care should be taken to bond the brackets somewhat occlusally in order to prevent their extrusion.

If a convertible band is used on the first molar, a step-up bend may be placed to intrude the second molar. When necessary, temporary anchorage devices, such as microscrews , may also be used to help intrude maxillary second molars. Converting a molar tube into a bracket. (a) Molar band with convertible buccal tube. (b) The buccal cap of the convertible tube is being removed; ligature cutters may be used to peel back the cap. (c) Buccal tube converted into a bracket. (d) Convertible tubes on the maxillary first molars are useful in situations in which continuous archwire mechanics are required to align or reposition malpositioned second molars. Converting the first molar tube into a bracket permits insertion of a continuous archwire with a step between the first and second molars, which would otherwise not be possible .

Buccal flaring of maxillary molars – Maxillary arch expansion tends to cause buccal flaring of the molars and resultant dropping down of their palatal cusps It is important to avoid buccal flaring of maxillary molars by not expanding too quickly, particularly with quadhelices , and using rectangular archwires with buccal root torque. Occasionally, the rather prominent palatal cusp tips of maxillary second molars may be reduced in height using a dental handpiece . (b) A buccally inclined maxillary second molar with hanging palatal cusp acting as an occlusal interference . (a) Buccal flaring (excessive buccal inclination) of maxillary molars

Buccal flaring (excessive buccal inclination) of maxillary molars may result in dropping down of their palatal cusps, which may cause an occlusal interference. Geometrically, the palatal cusp will only drop down after a small degree of rotation, following which it will elevate. Therefore, in clinical practice, what is likely to occur is overeruption of the molar following a small degree of buccal flaring. The combined buccal flaring and overeruption leads to an occlusal interference .

Avoidance of premolar extrusion – Accurate bracket positioning is always important, but its significance is magnified in orthognathic patients. Premolar extrusion usually results from incorrect bracket positioning . It is vital to avoid the relative extrusion of the premolar teeth, and if required, it is more cautious to bond these teeth slightly occlusally , and reposition them postoperatively. Mandibular right second premolar is extruded relative to the rest of the mandibular arch. If uncorrected, this will lead to an occlusal interference .

Overeruption – Any tooth may potentially overerupt . This is particularly true of maxillary posterior teeth when their antagonist is missing . These teeth should be re-intruded and levelled in relation to the rest of the arch as far as possible .

Temporary anchorage devices, such as microscrews , may prove particularly useful under these circumstances. Where significant overeruption has occurred, occasionally surgical repositioning of the dentoalveolar segment at the time of surgery may be required . use of five microimplants and modified TPA for selective intrusion of the maxillary dentoalveolar segment

Unopposed maxillary second premolar and molar are excessively over-erupted. The patient is being prepared for segmental maxillary surgery. As such these teeth must be levelled either with preoperative orthodontics or intraoperatively with a segmental relative dentoalveolar impaction .

Premolar–canine substitution – If tooth positions have to be substituted, e.g. severely ectopic maxillary canine removal and mesialization of the first premolar into the canine position, the premolar palatal cusp may have to be reduced in height. A severely crowded case, where unusually, four canines were extracted. The resulting occlusion gave acceptable contacts between first premolar and lateral incisors and improved the arch form. (a-c) Pre treatment, (d-f) Post treatment

Canine-lateral incisor substitution – If the maxillary lateral incisor is missing or has to be extracted, consideration may be given to substitution with the maxillary canine. Aesthetically, the parameters to consider are the gingival margin height on the canine, its colour and morphology, though the tip may be reduced and the shape of the tooth made more incisiform . However, the palatal surface of the canine, which is more prominent than a lateral incisor, may also need to be reduced to permit occlusion with the mandibular incisors .

Prominent cusp tips – The morphology of some teeth is such that their cusps may be long and pointed. Additionally, in some Class III patients normal attrition may not have occurred, so mandibular canines are often rather pointed and a potential interference. Minor enameloplasty of prominent canine tips will help achieve a better occlusion and is often an aesthetic enhancement .

Preparation for the preoperative ‘joint clinic ’ When the active phase of preoperative orthodontics has been completed, and the final preoperative archwires have been in position long enough to become passive (at least 4 weeks), the patient will have an appointment to obtain the preoperative records.

Preoperative radiographs – These should be taken only as required (OPT and lateral cephalometric radiograph are mandatory; periapical radiographs may be desired of regions where the surgical cuts for segmental surgery are planned; posteroanterior radiographs or 3D scans may be desired for complex asymmetries.

radiographs without the archwires in situ , enhancing visualization of the teeth, particularly on cephalometric radiographs, and permitting better cephalometric prediction tracings to be undertaken Some clinicians prefer to take these

Preoperative photographs – A complete set of facial and intraoral photographs are required .

‘Snap’ models – The impressions for these study casts should be taken without the archwires in situ , to allow better visualization of the teeth in three dimensions .

Planning predictions – If any form of prediction planning is used, it should be available for the surgeon to view at the joint clinic. Presurgical manual prediction , Incisor at rest line (2 mm below the upper lip ) and Rotating the mandible around the condyle, 2 mm upper to rest line . Reposition of maxilla on mandible unti l A superimposes on N.Perp line , Reposition of mandible to achieving maximum intercuspation and Postsurgical manual prediction .

Once these records have been taken, the patient will be seen on the preoperative ‘joint clinic’ for planning by the surgeon and orthodontist, together with the preoperative records. Having analysed the patient and their records, and agreed on the surgical plan, the patient is then booked two appointments with either the treating clinician or the maxillofacial technologist

1. For impressions (usually with the archwires in situ, to prevent the potential for the impression material moving the teeth), and facebow record as required, in order to undertake model surgery and make the surgical wafer splints – The completed model surgery should be checked by both the surgeon and the orthodontist, ideally together, before the final splints are made by the maxillofacial technologist .

2. Checking of wafer splints preoperatively for fit – These should be checked by the surgeon (or orthodontist) to ensure a good fit and no rocking . It is also useful to check the final wafer on the preoperative study models to check the proposed final occlusion .

Following the joint clinic and with the operation date set, the patient may also be booked for the immediate preoperative appointment with the orthodontist.

Immediate preoperative appointment This appointment should be ideally no more than 2–3 weeks prior to the date of the operation. The purpose of this appointment is: Checking brackets and bands – It is important to ensure that the brackets and bands are all secure .

Ligate brackets with stainless steel ligatures – All the brackets should be tied securely with stainless steel ligatures, except for self-ligating brackets, where ligatures are only required on a specific bracket if the orthodontist is concerned that the specific archwire engaging mechanism may not hold intraoperatively. Elastomeric ligatures are not acceptable, as they may dislodge intraoperatively and lodge into open surgical sites.

Ligating brackets with stainless steel ligatures in the immediate preoperative orthodontic appointment. (a) A stainless steel ligature, either 0.008 or 0.012-inch (0.2 or 0.3 mm) diameter, is used to tie each bracket by engaging under the tie-wings. (b) It is pulled using the Mathieu pliers and simultaneously pushed with a ligature tucker from the opposite side. (c) It is twisted until tight around the bracket, thereby holding the archwire securely in position. The excess wire is cut

. (d) The twisted end is tucked under the archwire and bracket wings, using the ligature tucker, for patient comfort and to prevent catching the surgeon’s fingers intraoperatively. (e) There should be no sharp points evident. (f) The mandibular incisor brackets should be ligated after placement of the midline surgical hook, otherwise placement of the hook will be difficult in this small region.

Additionally , when the surgeon places the intermaxillary fixation on the archwire hooks, steel ligatures prevent the archwire being pulled out of the bracket slot because of their inelasticity .

Placement of surgical hooks – A number of bracket systems have integrated hooks on some (usually the canine brackets) or all of the brackets. These are primarily for the use of the orthodontist in placement of elastics, and should be avoided by the surgeon intraoperatively while placing wire intermaxillary fixation, as this may debond the respective bracket.

Intermaxillary fixation should be placed on appropriately placed surgical hooks, either crimpable or soldered directly onto the archwire . When placing a crimpable surgical hook onto the archwire , it is important to gently squeeze the hook onto the archwire without any upward or downward movement of the wrist , in order to avoid debonding the brackets on either side, or inadvertently placing torque into the rectangular archwire .

Alternatively, the archwire may be marked intraorally, and removed to have hooks crimped or soldered (a, b) A crimpable surgical hook. (c) A crimpable hook held in the beaks of crimpable hook pliers. (d) Crimping a hook on a rectangular archwire . (e) A midline crimpable hook and bilateral soldered hooks on the surgical archwire .

Soldering of hooks are particularly useful if round archwires have to be used rather than rectangular archwires , e.g. in a patient prone to root resorption. Usually, each arch requires one midline hook and a hook between the premolars bilaterally. However, some surgeons prefer a greater number of hooks .

The maxillary midline hook sometimes catches the patient’s upper lip, and patients should always be provided with vegetable wax to place over this area if required. In the postoperative phase, both surgical hooks on the archwire and integrated hooks on brackets will be employed by the orthodontist for placement of both guiding and working elastics.

These specific ligatures are fabricated from either 0.012-inch (0.3 mm) or 0.014-inch (0.35 mm) annealed stainless steel wire, with the legs welded onto one another forming a helical hook at the end Placement of a Kobayashi ligature . Kobayashi ligatures may be used in place of the inter-bracket surgical hook .

Placement is as with conventional stainless steel ligatures, but the hook may be employed for elastic attachment by the orthodontist postoperatively. In some cases, where the inter-bracket span in the mandibular central incisor region is markedly reduced and a surgical hook cannot be crimped onto the archwire , or if a round archwire has to be used in place of a rectangular archwire (e.g. a patient prone to root resorption where rectangular archwires have to be avoided), Kobayashi ligatures may be used in place of the inter-bracket surgical hook.

The surgeon will need to take extra care not to debond the mandibular incisor brackets intraoperatively while placing the IMF. Otherwise, these ligatures are for the use of the orthodontic elastics, not IMF.

It is also important for the orthodontist to put aside enough time to discuss any final issues with the patient. Despite previous information provision, patients may still have some questions at this stage .

Finally, patients will be understandably anxious at this close stage to the operation, and the orthodontist should reassure the patient that they will be in the safe hands of an experienced surgeon and anaesthetist .

Preoperative orthodontics for orthognathic surgery

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Preoperative orthodontics for orthognathic surgery

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